Cate sits up very well with assistance (leaning against something or with pillows around her in case she starts to lose her balance) and can sit unassisted for about 30 seconds on her own. The last time she went grocery shopping, she was very frustrated to be in her infant carrier in the cart (not to mention that her carrier doesn't fit very well in the small carts at Whole Foods where we've been doing most of our shopping for the last 6 weeks or so). So I decided to try her in the big kid seat in the cart with her grocery cart cover. There's a back support that you can't really see and she was strapped in- both of which helped to stabilize her better. She smiled the whole time and seemed to enjoy the view (and being close to mom). We picked up some rice rusks while we were there (Baby Mum Mum is the brand for those of you looking for a good rice cracker for a new-to-foods infant). The rusk dissolved quickly as she gummed it and wasn't too messy. She enjoyed it as well.
She's doing new things each and every day and we never cease to be amazed by her.
Tooth update: One lower one has pushed through the gums, but is not all the way up. We feel another bump lurking below her gums right next to it.